This invention relates to an intake control system for engines and more particularly to an improved induction system for internal combustion engines.
It has been proposed to increase the power output of an internal combustion engine by providing multiple intake passages, each serving the same chamber of the engine. By virtue of the use of such multiple intake passages the volumetric efficiency at wide open throttle may be improved, and, accordingly, maximum power output can be achieved. However, the use of such multiple intake passages provides problems with low speed running. That is, the gas velocity through the increased induction passage area is so slow at low and mid-range speeds that poor performance is encountered. Therefore, it has been proposed to provide some form of throttle valve arrangement for controlling the flow through the intake passages so that less than the maximum effective area is employed at low speed running. Such an arrangement increases the gas velocity at low speeds and can significantly improve low speed running. Examples of such arrangements are shown in Japanese Patent SHO 47-32850, Japanese published utility model application SHO 54-97620, and Japanese laid open patent application SHO 55-551920. It has been found, however, with the previously proposed throttle controlling mechanisms that performance is deteriorated at least certain running conditions. For example, it has been found that the previously proposed throttle controlling arrangements actually result in a reduction in mid-range torque due to the fact that the throttle controlling arrangement restricts air flow under these conditions. It has been found that the throttle valve control is not sufficient to avoid the generation of pulsations in the intake system under this running condition which pulsations reduce charging efficiency and provide a loss in mid-range torque. Furthermore, the previously proposed throttle valve arrangements may actually result in some decreases in low speed torque as well.
It is, therefore, a principal object of this invention to provide an improved induction system for an internal combustion engine.
It is a further objection of the invention to provide an induction system that improves the torque characteristics throughout the entire engine speed and load ranges.
It is another object of this invention to provide an improved throttle valve arrangement for an engine having an induction system consisting of multiple intake passages for each chamber of the engine.
It is yet a further object of this invention to provide a throttle valve arrangement for a multiple intake passage induction system that improves the torque throughout the engine speed and load ranges.